The surface of the Earth is a Dangerous Place to Live

Map of recent earthquakes USA

Map of recent earthquakes World

The composition of the earth reflects the processing of elements by stars. The earth was originally molten and hence seperation of light and heavy elements occurred in the earth's gravitational field. Heavy stuff sinks to the core; light stuff floats and cools to form the crust

Plate Tectonics means that the crust of the earth is divided into large connected units, all of which are moving relative to one another:

The Electronic Universe Project